Pickling solution



I Patented Dec. 15, 1931 UNITED STATES PATENT OFFICE FLINT C. ELDER, OF CLEVELAND HEIGHTS, CLEVELAND, OHIO PICKLING SOLUTION R0 Drawing. Application filed. July 7,

This invention relates to a pickling solution and, while not limited to the cleaning of any particular type of metal, is particularly adapted for cleaning what is commonly known in the art as stainless steel or alloy steels which have embodied therein chromium and nickel in suitable proportions to produce a steel which will resist corrosion.

Among the plckling solutions which have been used for cleaning the above type of metal may be mentioned hot sulfuric acid and water; muriatic acid of different concentrations and temperatures followed by dipping in a hot solution containing nitric acid; and a solution of caustic soda and sodium permanganate.

The objection to the hot sulfuric acid solution is that it leaves the steel with ablack smut which apparently contains some chromium oxid as it rapidly cuts out the dies and spoils the finish. The muriatic acid solution followed by dipping in nitric acid causes surface pitting of the steel, especially cold rolled steel, resulting in a poor finish, and the caustic soda and sodium permanganate solution is open to the same objection.

The object of the present invention is to provide a pickling solution which will clean the metal quickly and therefore economically and which, at the same time, will give a,

bright, smooth surface to the cleaned steel. It has been found that this result may be obtained by adding a certain percentage of soluble copper salt to an acid solution. In cleaning alloy steels containin 18 per cent chromium and 8 per cent. nic el, a 10 per cent. aqueous solution of sulfuric acid (10 per cent. by volumne of H SO, plus 90 per cent. water) containing 10 per cent. copper sulphate crystals (CuSO '5H O) used at a range of temperature from 160 degrees to 200 degrees Fahrenheit or slightly higher, has been found to produce satisfactory results. Copper chloride in a muriatic acid solution will produce satisfactory results as will copper chloride in a sulfuric acid solution.

The action of the solution on stainless steel is quite active but soon ceases, due to precipi- 1930. Serial No. 466,343.

face from further action but which can be easily wiped or brushed off in water. With the above formula a strip of annealed cold rolled steel can be cleaned in approximately ten seconds, leaving a smooth, shiny surface free from pitting.

I claim:

1. A- pickling solution for stainless steel consisting of a 10 per cent. aqueous solution of sulfuric acid 10 per cent. by volume of 60 H SO plus 90 per cent. water) and 10 per cent. copper sulphate crystals 1 (CuSO.5H O). 2. A pickling solution for stainless steel consisting of an aqueous solution of pickling acid and approximately 10 per cent. of solu- 60 H SO, plus 90 per cent. water) and apprloximately 10 per cent. of soluble copper sa ts.

5. The process of cleaning stainless steel which consists in dipping the steel in an acid pickling solution containing approximately 10 percent. of soluble copper salts brought to a temperature of 160 degrees Fahrenheit or higher.

6. The process of cleaning stainless steel i which consists in dipping the steel in a sulfuric acid pickling solution containing approximatelylO per cent. of copper sulphate and brought to a temperature of 160 degrees Fahrenheit or higher.

In testimony whereof, I have hereunto set my hand.

FLINT C. ELDER.

CFOSS HGTBI'BHCB Examiner 

